Preliminary results from our laboratory indicate that the functional mRNA content of a specific protein (SMP-2) in rat liver shows dramatic changes during aging. The mRNA for SMP-2 is found in high concentration in the liver of prepubertal male rats. It disappears after puberty and again reappears at senescence. Based on this preliminary observation, we feel that SMP-2 can serve as an important marker for the study of hormone action and aging. The initial phase of the proposed research will involve isolation of SMP-2, production of monospecific antiserum and development of a sensitive radioimmunoassay for this protein. Second phase of the project will involve purification of SMP-2 mRNA and synthesis of a cDNA probe. Double stranded SMP-2 cDNA will be cloned in E. coli and pure cloned cDNA probe will be isolated. The monospecific antibody to SMP-2 and the cloned cDNA probe will be used to investigate the mechanism of the hormone and age dependent regulation of the SMP-2 gene. Hormonal regulation of SMP-2 will be followed by a correlative study involving the induction and repression of SMP-2 and its mRNA under various endocrine conditions which are known to specifically affect SMP-2 synthesis and cause changes in the synthesis of other hepatic proteins (e.g. castration, hypophysectomy and diabetes). Relative ratio between hybridizable and translatable SMP-2 mRNA will be correlated to the amount of intracellular SMP-2 and its rate of synthesis. Age dependent changes in the hepatic androgen and estrogen receptor activity and its effect on the synthesis of SMP-2 and its mRNA will also be explored. Results of this investigation are expected to provide new insights into the molecular mechanism of the aging process in relation to changing endocrine environment. In addition, the system will also provide a well-characterized model system for the study of molecular biology of estrogen and androgen action on a specific gene expression in the mammalian liver.